The present invention relates to methods of manufacturing single crystal which is widely used as a superconducting element, a semiconducting element or an optoelectronic element in the electronics industry and the like.
BaPb.sub.1-x Bi.sub.x O.sub.3 (barium-lead-bismuth oxide) having Pervoskite structure, shows superconductivity in the range of 0.05&gt;x.ltoreq.0.30, semi-metallic characteristics in the range of x&lt;0.05, and semi-conductivity in the range of 0.30&lt;x. The maximum super-conductive transition temperature Tc a 13K when X is approximately 0.25. This is the highest known temperature at which an oxide material that does not include transition metal elements exhibits the super-conductivity. Attention has focussed on these barium-lead-bismuth oxide compounds because of their super-conductivity and because the superconductivity depends on their exact composition. Further, the compounds of this series include semi-metallic materials and its carrier density N(O) at Fermi surface is extraordinarily small as a super-conductor. Therefore, these compounds have a resistance rate that is several orders of magnitude greater than ordinary metal super-conductors, at temperatures slightly higher than Tc. This characteristic is required for materials used for superconductive switches. When barium-lead-bismuth oxide compounds are formed as single crystals, they are relatively stable and crystals which are transparent in the infra-red region, can be expected to be useful for optical electronics elements at very low temperatures.
Conventionally, the growth of BaPb.sub.1-x Bi.sub.x O.sub.3 single crystal is carried out by the crystallization utilizing a flux. According to one method, KCl can be utilized as the main conponent of the flux. KCl flux is favorable as a flux to dissolve BaPb.sub.1-x Bi.sub.x O.sub.3, but to dissolve KCl and to melt KCl in BaPb.sub.1-x Bi.sub.x O.sub.3, a high temperature of about 1000.degree. C. is necessary, and thus potassium ion remains within BaPb.sub.1-x Bi.sub.x O.sub.3 single crystal, and thus the impurity density becomes large. Also, as the material grows at a temperature higher than the transition point of BaPb.sub.1-x Bi.sub.x O.sub.3, the point existing in a range from 500.degree. C. to 600.degree. C., crystal phase transition occurs during cooling down, and therefore, a strain largely occurs within the crystal.
There is another method utilizing PbO.sub.2 --Bi.sub.2 O.sub.3 --BaPbO.sub.3 solution which is a non-stoichiometric compound solution. In this case, there is an advantage that the enclosure of the impurity material will lessen greatly, but, when crystallizing BaPb.sub.1-x Bi.sub.x O.sub.3 from the non-stoichiometric compound, control of the composition factor x that determines the characteristics of the material, is very difficult. Also, a strain accompanying as phase transition, occurs the stated above.
Technology of the above prior art is disclosed in the following document, Akinori Katsui; Japanese Journal of Applied Physics Vol. 21 No. 9 (1982) Pages 553 to 554.
In accordance with the conventional method of manufacturing BaPb.sub.1-x Bi.sub.x O.sub.3 single crystal, the impurity density within the material is large, and also, the change of composition factor x in the material is great. Also the conventional method has various problems, such as the reappearance characteristic of composition x is bad, and the phase transition occurs, and the heat strain remains because of the high temperature growth process at about 1000.degree. C., and these problems are the major factors that prevent the sharp transition to the super-conductivity of the material.
The inventors have invented and filed the related application Ser. No. 837,515) with respect to a method of manufacturing BaPb.sub.1-x Bi.sub.x O.sub.3 single crystal grown by hydrothermal synthesis using a chloride aqueous solution.